double calculate$\_$bill$($char $*$in$\_$file, char $*$customer$)$;

This function will open the file named in file, read the data, and calculate and return the

bill of the customer specified by customer. In case of errors, your function should return an

appropriate error code as described in section $4\mathrm{.}4.$

The formula to calculate the bill b per row is given by

b $=0\mathrm{.}01$ n $+0\mathrm{.}02$ s $+0\mathrm{.}06$ x $$ t

where n is the network usage in megabytes, s is the storage usage in blocks, x is the number of

servers used, and t is the number of hours the service is run. The bill is simply the sum of the

bills of each relevant row.

For example, for the input file

$01/01/2000|$Science$|5|3\mathrm{.}3|71|2/6$

$01/01/2000|$Engineering$|1|1\mathrm{.}3|25|1/3$

$01/02/2000|$Science$|7|1\mathrm{.}5|97|4/15$

for customer Science, the total bill is $3\mathrm{.}72$