Which expression corresponds to the graph at the right? please help me with the question in the picture

The graph below shows the price of different numbers of mats at a store: a graph is shown. the values on the x axis are 0, 2, 4, 6, 8, 10. the values on the y axis are 0, 21, 42, 63, 84, and 105. points are shown on ordered pairs 0, 0 and 2, 21 and 4, 42 and 6, 63 and 8, 84. these points are connected by a line. the label on the x axis is number of mats. the title on the y axis is price in dollars. which equation can be used to determine p, the cost of b mats?

Which has the greater energy, light of wavelength 519 nm or light with a frequency of 5.42 x 10^8 sec^-1?

The product of 3 and a number increased by 8 is 31