Applications of periodic functions : tides and times

On a typical day at a seaport, the water has a maximum depth of 16 m at 7:00 AM. The minimum depth of 4m occurs at 1:24 PM. Assume that the relation between depth *h*, in metres, and the time *t, *in hours, is a sinusoidal function.

a) write an equation for *h* for any time, *t* hours.

My answer: $\displaystyle h= 6 {\cos}\frac{\pi}{6.4}(t-7)+10$ (in radians)

b) Give the depth h at 10:30 QM (accurate to two decimals)

My Answer: 10:30 = 10.5 hours, I punched my equation into my TI-83 Plus and I got 9.12 as the value

c) find two times before noon when h is 14m (accurately to the nearest minute)

Here's my problem; I punched in a second equation $\displaystyle y_{2}= 14$ and then found the intersects, but I that gives me decimals which are not as simple to convert from hundredths of hours to minutes. How can I make the conversion easily? and am I going about this question correctly?