Martina makes house calls. For each, she is paid a base amount and makes additional money for each hour she works. The graph below shows her pay (in dollars) versus the number of hours worked. Use the graph to answer the questions. 200- . .. .. ... .......... 180- .. i .. 160- . . ! . . 140- . .i . . .... . . . . 120- Pay ($) 100- J.... .... . . . . . . . . . .;.. L . . .. ..i.. . . . .. . . . . 20 ..:.. -.!... ... . ... Number of hours worked(a) How much does her pay increase for each hour worked? (b) What is the slope of the line