Answer:
c) The total price for the service  when Terrance's price was equivalent to Sylvester's price  is $600.
Step-by-step explanation:
    Here,    t = 320.00 + 0.40 b
and  t = The total prices charged by Terrance for packing and moving b boxes.
 s = 250.00 +0.50 b
and  s = The total prices charged by Sylvester  for packing and moving b boxes.
Now, to find the number of boxes, when both the prices are equal.
⇒320.00 + 0.40 b  = 250.00 +0.50 b
or, 320 - 250 = 0.50 b - 0.40 b
or, 0.10 b =  70
or, b= 70/0.10 = 700
Hence, for packing and moving b = 700 boxes, both companies charge the same amount.
Now, the price charged = 320 + 0.4 (b)
                                          = 320 + 0.4(70) = 320 + 280 
                                          = 600
or,  the total price for the service  when Terrance's price was equivalent to Sylvester's price  is $600.