John can type a set of pages in 5 hours at a constant rate. If John types for 3 hours and Jack does the rest of the job, who works at 2/5 constant rate of John. How long will it take for Jack alone to do the rest of the job? Choose the correct choice from the following options:  A) 1 hrs  B) 3 hrs  C) 4 hrs  D) 5 hrs  E) 7 hrs

Rationale: john will do 3 / 5 in 3 hrs , so john does 3 / 5 of the work . . therefore , jack will do the remaining 2 / 5 th work alone . . as the speed of jack is 2 / 5 rate of john , jack will do the 2 / 5 th work in same time that john takes to complete full job . . . ans 5 d
Answer: D