The table below shows a firm's output per day for zero through six workers. ...

a.       
Marginal product is change in total product from one more worker.

      Q   L   MP   
   0   0   —
   46   1   46
   84   2   38
   114   3   30
   136   4   22
   150   5   14
   156   6   6

b.       
MRP = MR ∙ MPL       
We must determine MR at levels of output corresponding to one through six workers.         

MR    =    50 - 0.25Q   =   
MR(46)    =    50 - 0.25(46)     =    38.50
MR(84)    =    50 - 0.25(84)     =    29.00
MR(114)    =    50 - 0.25(114)    =    21.50
MR(136)    =    50 - 0.25(136)    =    16.00
MR(150)    =    50 - 0.25(150)    =    12.50
MR(156)    =    50 - 0.25(156)    =    11.00

   MRP = MR ∙ MPL

      L   Q   MP   MR   MRP   
   1   46   46   38.50   1771
   2   84   38   29.00   1102
   3   114   30   21.50   645
   4   136   22   16.00   352
   5   150   14   12.50   175
   6   156   6   11.00   66

c.       
The firm would want to hire every worker whose MRP > W.  Thirty dollars per hour is $240 per day.  The firm would want to hire four workers.