Example 1Take a look at Examples 1 and 3 in the text.Example 1Total CostYour cellular phone company offers you an innovative pricing scheme. When you make a call, the marginal costof the t-th minute of the call will bec(t) = 20/(t + 100) $/min.Use a numerical calculation to estimate the cost of a 60 minute phone call.SolutionAs we see in the text, the total cost is given by the definite integral,Computing this integral numerically amounts to breaking the interval [0, 60] into a large number of shortintervals, and adding up the costs over these intervals. The smaller the interval, the more accurate the answer.Thus, let us begin by deciding on the number of divisions we will use, and setting up all the values of t.n120The number of subdivisionsa0The start of the time-interval (lower limit of integration)b60The end of the time-interval upper limit of integration)Delta t0.5The width of each subinterval, given by (b-a)/n (look at its formula -- do not change this value)tc(t)c(t)*Delta tRiemann Sumt starts at a.0Add Delta t1.We will fill in the t-column with values starting at a = 0.at each step.and continuing in steps of Delta t.We would like to be able to change n without changing thelength of the columns each time, so we will use a trick:Instead of worrying about stopping when you reach b,let t go on for 1000 or so steps (or the largest value of nyou are interested in), and then set c(t) = 0 if t >= b, sincewe don't want to sum terms c(t) if t >= b (see the text).2.(Test your formulas by changing n, a, and b.)Go down forNow fill in the formula for c(t). However, instead of using1000 or so=20/(t+100)steps.we will use=IF(t