Problem $2-(7$ points maximum$).$ The following $1-$h hyetograph was measured at a location in Atlant Georgia. The measurement was made in a $4,000m^2$ urban watershed. From historical records of precip and runoff, the average $-$index was also reported to be $2c\frac{m}{h}.$

TIME INTER VALS

$[$minutes$,$ min $]$

$0-20$

$20-40$

$40-60$

RAINFALL

$[$centimeters per hour, $c\frac{m}{h}]$

$4\mathrm{.}0=$

$8\mathrm{.}0=$

$6\mathrm{.}0=$

a$)(3$ points$).$ Plot the storm hyetograph for intensity $($in $c\frac{m}{h})$ as function of time $($in min or $h)$; present your plot. Label both the ordinate and abscissa with the correct variables and units.

b$)(4$ point$).$ Draw the $-$index on the plotted hyetograph of the previous question and determ: amount of rainfall excess or direct runoff, in $cm,$ over the $1-h$ duration of the storm.