Assume that a computer can carry out an LU-factorization of a 5000x5000 matrix in 1 second. How long will it take to solve 100 problems =Ax=b, with the same 3000x3000 matrix A and 100 different b?

a) 0.2376

b) 2.1600

c) 0.2160

d) 0.2268

What is the 1-norm of x=[1, -3, 4]?

a) sqrt(26)

b) 2

c) 8

d) 4