Length of the day light( in hours) is, $\"\"$ .

Find the rate of change of the function.

$\"\"$

Differentiate on each side with respect to $\"\"$ .

$\"\"$

Consider the rate of change of length of the day light.

$\"\"$

March 21 is 81st day of the year.

Hence to find the rate of change 80th day.

Substitute $\"\"$ in $\"\"$ .

$\"\"$

$\"\"$ hours/day.

Number of hours of day light is increasing on march 21 is 0.0482.

May 21 is 141st day of the year.

Hence to find the rate of change 140th day.

Substitute $\"\"$ in $\"\"$ .

$\"\"$

Number of hours of day light is increasing on may 21 is 0.0240.

$\"\"$ .

(a) Number of hours of day light is increasing on march 21 is 0.0482.

(b) Number of hours of day light is increasing on may 21 is 0.0240.