Let T_i = Normal Completion Time for Task IR_i = $\Sigma$

Multiple Choice

Let T_i = normal completion time for task iR_i = crash completion time for task i C_i = normal cost for task i
H_i = crash cost for task i
X_i = start time for task i
Y_i = amount of time by which task i is to be crashed.
What is the objective function of a linear programming model for project crashing?

A) $\Sigma$ _{all i} Y_i(H_i - C_i) /(T_i - R_i)
B) $\Sigma$ _{all i on critical path} Y_i(H_i - C_i) /(T_i - R_i)
C) $\Sigma$ _{all i} X_iY_i
D) $\Sigma$ _{all i} Y_iH_i