C :

#include <stdio.h>
#define MOD 200907

long long g(long long q, long long k) {
    long long sum = 1, a[1000], i = 0;
    while (k) {
        if (k % 2 != 0)
            a[i++] = 1;
        else
            a[i++] = 0;
        k /= 2;
    }
    i--;
    for (i; i >= 0; i--) {
        sum = (sum * sum) % MOD;
        if (a[i])
            sum = (sum * q) % MOD;
    }
    return sum % MOD;
}


int main() {
    long long a, b, c, k, t, d, q;
    int n;
    scanf("%d", &n);
    while (n--) {
        scanf("%lld%lld%lld%lld", &a, &b, &c, &k);
        if (b - a == c - b) {
            d = b - a;
            t = ((((k - 1) % MOD) * (d % MOD)) % MOD + a % MOD) % MOD;
            printf("%lld\n", t);
        } else {
            q = b / a;
            printf("%lld\n", (a % MOD * g(q, k - 1)) % MOD);
        }
    }
    return 0;
}

C++ :

#include <stdio.h>
#define MOD 200907

long long g(long long q, long long k) {
	long long sum = 1, a[1000], i = 0;
	while (k) {
		if (k % 2 != 0)
			a[i++] = 1;
		else
			a[i++] = 0;
		k /= 2;
	}
	i--;
	for (i; i >= 0; i--) {
		sum = (sum * sum) % MOD;
		if (a[i])
			sum = (sum * q) % MOD;
	}
	return sum % MOD;
}
int main() {
	long long a, b, c, k, t, d, q;
	int n;
	scanf("%d", &n);
	while (n--) {
		scanf("%lld%lld%lld%lld", &a, &b, &c, &k);
		if (b - a == c - b) {
			d = b - a;
			t = ((((k - 1) % MOD) * (d % MOD)) % MOD + a % MOD) % MOD;
			printf("%lld\n", t);
		} else {
			q = b / a;
			printf("%lld\n", (a % MOD * g(q, k - 1)) % MOD);
		}
	}
	return 0;
}