63. Find the equation of 1hc curve that passes through (2, 3:1 if its slope is given by (1')! =4_ 3 dx x for each x. 81. Marketing. An automobile company is ready to introduce a new line of hybrid cars through a national sales campaign. After test marketing the line in a carefully selected city, the marketing research department estimates that sales (in millions of' dollars) will increase at the monthly rate of s"(r)=10 1050-\" 0 5:1: 24 t months after the campaign has started. (A) What will be the total sales S( r) t months after the be- ginning of the national campaign if we assume no sales at the beginning of the campaign? (B) What are the estimated total sales for the rst 12 months of the campaign? (C) When will the estimated total sales reach $100 million? Use a graphing calculator to approximate the answer to two decimal places. 53. Show that y = 1 - Ce *is a solution of the differential equation dy/dx = 1 - y for any real number C. Find the particular solution that passes through (0, 0). 54. Show that y = Ce* - 1 is a solution of the differential equation dy/ dx = y + 1 for any real number C. Find the particular solution that passes through (0, 0). 55. Graph the particular solution found in Problem 53 in the ap- propriate Figure A or B (or a copy).