To what time complexity classes does the following loops belong to? Motivate the answers carefully!

a)

for (s = 0; is< n; t++)

for (t = 0; t < n; j++)

x[s]tj] = y[s][t] + z[s][t];

b)

for (s = 0 ; i < n ; s++)

for (t = 0 ; j < n ; t++)

for (u = a[s][t] = 0 ; u < n ; k++) a[s][t] += b[s][u] * c[u][t];

c)

for (knt = 0, s = 1 ; s <= n ; s++)

for (t = 1 ; t <= i ; t++)