A street light is 12 feet above a straight bike path. Olav is bicycling down the path at a rate of 15 MPH. At midnight, Olav is 39 feet from the point on the bike path directly below the street light. (See the picture.) The relationship between the intensityCof light (in candlepower) and the distanced(in feet) from the light source is given byC= (k/d^2), wherekis a constant depending on the light source.

Attachment 25663

a) From22 feet away, the street light has an intensity of 1 candle. What isk?

22^2 = k = 484

b) Find a function which gives the intensityI of the light shining on Olav as a function of timet, in seconds.

So below is the answer for "b" but I am confused on how to get this, can someone explain to me? Thank you!