Assume that a computer can carry out an LU-factorization of a 5000x5000 matrix in 1 second. How long will it take to solve 50 problems Ax=b, with the same 4000x4000 matrix A and 50 different b?

a) 0.5120

b) 0.5248

c) .05312

d) 0.5216

what is the infinite norm of matrix [2 -1 6] [-2 5 3] [3 2 7]

a) 12

b) 7

c) 10

d) 16