Assignment of Tasks

You have $N$ tasks, indexed $1$ to $N$, where the $i$-th of which takes $A_i$ time to be completed by a skilled worker, and can be started only after the time $S_i$ (including exactly at $S_i$). You have $M$ workers, indexed $1$ to $M$, where the $i$-th of which has a skill deficiency factor of $F_i$ meaning that if a skilled worker would take $t$ time to complete the task, this worker will take