The answe is $9748$ How do i get to that?

$1\mathrm{.}7$ A reinforced$-$concrete culvert has to be designed for a roadway. The flood$-$frequency data at the proposed site are given in the table on the following page. The flood damages associated with various magnitudes of floods are also indicated in the table. A culvert of $30in.$ diameter will pass a discharge of $40cfs.$ Determine the total annual cost of this culvert including the cost of damage due to higher than design$-$level floods. Assume that the following relationships hold for annual direct cost and cost of operation and maintenance: $(1)$ Annual direct cost $=950+70D(D$ is diameter in inches$)$ and $(2)$ Annual O&M cost $=30\%$ of direct cost.