Here is a table given try to understand and give me the answer.Table is divided into two parts. on the left side there is three columns Activity Id$,$ Slope and Maximum crash time. Under these three there are $7$ rows. Under Activity Id:A$,$ B$,$ C$,$ D$,$ E$,$ F and G$.$ Under Slope: $$20,$ $$40,$ $$30,\_\_\_\_($blank$),$ $$30,$ $$30$ and $0.$ Under maximum crash time: $1,2,1,\_\_\_\_($blank$),2,1,0.$ Now on the right side there is one main heading Direct Costs which further divides into two categories Normal and Crash. Under Normal there are two columns, Time and Cost, both have $7$ rows. Under Time rows are: $3,6,10,11,8,5$ and $6.$ Under Cost: $$50,$ $$80,$ $$60,$ $$50,$ $$100,$ $$40,$ $$70.$ NOW on the Crash side which is also divided under two categories Time and Cost. Under time : $2,4,9,7,6,4,6.$ Under Cost: $$70,$ $$160,$ $$90,$ $$150,$ $$160,$ $$70$ and $$70.$ So its all about the table.So now What is the Maximum Crash time of Activity D:$$40$ b$.$ $$25$ c$.$ $$20$O d$.$ $$30$