【HDU 4602】Partition

#include<cstdio>
#define ll long long
ll m=1e9+7;
ll qpow(int b)
{
    ll a=2,ans=1;
    while(b)
    {
        if(b&1)ans=ans*a%m;
        a=a*a%m;
        b>>=1;
    }
    return ans;
}
int main()
{
    ll t,n,k;
    scanf("%lld",&t);
    while(t--)
    {
        scanf("%lld%lld",&n,&k);
        if(n<k)
            printf("0\n");
        else if(n==k)
            printf("1\n");
        else if(n-k==1)
            printf("2\n");
        else
            printf("%lld\n",(n-k+3)*qpow(n-k-2)%m);
    }
    return 0;
}