Step-by-step explanation:
Circle:
diameter = 30 ft
r = 30/2 = 15 ft
Area = πr²
     = 3.14 * 15*15
     = 706.50 square feet
Triangle:
base (b) = 30 ft
height (h) = 20 ft
Area =
   Â
    = 300 square feet
Area of four triangles  = 4 * 300
                  = 1200  square feet
Area to be painted blue = area of circle + area of 4 triangles
                    = 706.50 + 1200
                    = 1906.50 square feet
Area painted by one bucket blue paint  = 350 sq. feet
Number of paint buckets needed = 1906.50 ÷ 350
                            = 5.44
                            = 6
6 buckets of blue paint is needed.
Cost of 6 buckets of blue paint = 85.50 * 6
                          = $ 513
Each part of the design needs two coats.
So Cost for  two coats = 2 * 513
                   = $ 1026
Square:
Side  =  40 ft
Area of square = side *side
             = 40*40
             = 1600 sq. ft
Area of square to be painted yellow = area of square - area of circle
                              = 1600 - 706.50
                             = 893.50 sq.ft
Area painted with  one bucket of yellow paint = 250 sq. ft
Number of yellow paint buckets needed = 893.50 ÷ 250
                                  = 3.574
                                  = 4
4 buckets of yellow bucket is needed
Cost of 4 buckets of yellow bucket = 64.50 * 4
                             = $ 258
Each part of the design needs two coats.
So Cost for  two coats = 2 * 258
                   = $ 516