Data Sufficiency

Guy's net income equals his gross income minus his deductions. By what percent did Guy's net income change on January 1, 1989, when both his gross income and his deductions increased?
(1) Guy's gross income increased by 4 percent on January 1, 1989.
(2) Guy's deductions increased by 15 percent on January 1, 1989.

1) and 2) are not sufficient by themselves.

together,
% change in N= G(1.04-1)- D(1.15-1)/(G-D)
=> (0.04G-0.15D)/(G-D) cannot be solved
not sufficient

hence, E

cannot be determined => hence option E