99. Cost, Revenue, and Profit A roofing contractor
purchases a shingle delivery truck with a shingle
elevator for $42,000. The vehicle requires an average
expenditure of $9.50 per hour for fuel and maintenance,
and the operator is paid $11.50 per hour.
(a) Write a linear equation giving the total cost C of
operating this equipment for t hours. (Include the
purchase cost of the equipment.)
(b) Assuming that customers are charged $45 per hour
of machine use, write an equation for the revenue R
obtained from t hours of use.
(c) Use the formula for profit P = R C to write
an equation for the profit obtained from t hours
of use.
(d) Use the result of part (c) to find the break-even
point that is, the number of hours this equipment
must be used to yield a profit of 0 dollars.