C arrays excercise

#include <stdio.h>
#include <stdbool.h>

bool exists(int *array, size_t array_length, int value);
size_t count_common(int *array_a, size_t size_a, int *array_b, size_t size_b);
int* differences(int *array_a, size_t size_a, int *array_b, size_t size_b);

bool multiple(int *array, size_t array_length, int value);
size_t count_multiples(int *array_a, size_t size_a, int *array_b, size_t size_b);
int* multiples(int *array_a, size_t size_a, int *array_b, size_t size_b);

int main()
{
    size_t size_a, size_b;
    printf("Insert the length of the two arrays: ");
    scanf("%d%d", &size_a, &size_b);

    int *array_a = malloc(sizeof(int) * size_a);
    int *array_b = malloc(sizeof(int) * size_b);

    // Filling A
    printf("Filling A: \n");
    for(size_t i = 0; i < size_a; i++) {
        scanf("%d", &array_a[i]);
    }

    // Filling B
    printf("Filling B: \n");
    for(size_t i = 0; i < size_b; i++) {
        scanf("%d", &array_b[i]);
    }

    int elements_found = count_common(array_a, size_a, array_b, size_b);
    int *array_found = differences(array_a, size_a, array_b, size_b);

    // Prints the result
    printf("Printing b in B but not in A: \n");
    for(size_t i = 0; i < elements_found; i++) {
        printf("%d ", array_found[i]);
    }

    int multiples_found = count_multiples(array_a, size_a, array_b, size_b);
    int *array_multiples = multiples(array_a, size_a, array_b, size_b);

    // Prints the result
    printf("\nPrinting b MOD a for each element of B and A: \n");
    for(size_t i = 0; i < multiples_found; i++) {
        printf("%d ", array_multiples[i]);
    }
    return 0;
}

bool exists(int *array, size_t array_length, int value) {
    for(size_t i = 0; i < array_length; i++) {
        if(array[i] == value)
            return true;
    }
    return false;
}

size_t count_common(int *array_a, size_t size_a, int *array_b, size_t size_b) {
    size_t elements_found = 0;
    for(size_t i = 0; i < size_b; i++) {
        if(!exists(array_a, size_a, array_b[i]))
            elements_found++;
    }

    return elements_found;
}

int* differences(int *array_a, size_t size_a, int *array_b, size_t size_b) {
    // Count the amount of differente values between A and B
    int elements_found = count_common(array_a, size_a, array_b, size_b);

    // array_found of the size of the elements found
    int *array_found = malloc(sizeof(int) * elements_found);
    elements_found = 0;
    for(size_t i = 0; i < size_b; i++) {
        if(!exists(array_a, size_a, array_b[i]))
            array_found[elements_found++] = array_b[i];
    }

    return array_found;
}


bool multiple(int *array, size_t array_length, int value) {
    for(size_t i = 0; i < array_length; i++) {
        if(value % array[i] == 0)
            return true;
    }
    return false;
}

size_t count_multiples(int *array_a, size_t size_a, int *array_b, size_t size_b) {
    size_t elements_found = 0;
    for(size_t i = 0; i < size_b; i++) {
        if(multiple(array_a, size_a, array_b[i]))
            elements_found++;
    }

    return elements_found;
}

int* multiples(int *array_a, size_t size_a, int *array_b, size_t size_b) {
    // Count the amount of differente values between A and B
    int elements_found = count_multiples(array_a, size_a, array_b, size_b);

    // array_found of the size of the elements found
    int *array_found = malloc(sizeof(int) * elements_found);
    elements_found = 0;
    for(size_t i = 0; i < size_b; i++) {
        if(multiple(array_a, size_a, array_b[i]))
            array_found[elements_found++] = array_b[i];
    }

    return array_found;
}