Urgent physics help (rotating vertical bar)

I found this problem very recently on the forum but mine seems to have a 4th and fifth part to it

http://img.photobucket.com/albums/v6...Untitled-1.jpg

The diagram shows a small ball of mass m=0.280kg that is attached to a rotating vertical bar by means of two massless strings of equal lengths L=1.10m. The distance between the points where the strings are attached to the bar is D=1.50m. The rotational speed of the bar is such that both strings are taut and the ball moves in a horizontal circular path of radius R at constant speed v=6.66m/s.

(a) Determine the magnitude and direction of the net force that is acting on the ball when it is in the position shown in the diagram.

(b) Determine the magnitude of the tension T1 in the upper string and the magnitude of the tension T2 in the lower string.

(c) Determine the speed of the ball at which the tension T2 becomes zero.

(d) Determine the angle of the top string when the velocity is v = 1.48 m/s.

(e) Determine the tensions T1 and T2 as a function of velocity (2 seperate equations).

I've already got the answers to a, b, and c, just need d and e.