The linear programming problem (P1)

max sum(cjxj)
s.t. 7/4(x1) - 2/3(x2) + 5/2(x3) - 5/12(x4) + 19/6(x5) = 7/4
x1,x2,x3,x4,x5 are all positive integers

And I need to show that the problem (P2) below is a relaxtion of (P1)

max sum(max{cj,0}xj)
s.t. 3/4(x1) + 1/3(x2) +1/2(x3) + 7/12(x4) +1/6(x5) = 3/4 +u
u,x1,x2,x3,x4,x5 are all positive integers.

Any help would be appreciated, thanks!