To be considered safe for ocean sailing, the capsize screening value C should be less than 2 For a boat with a beam (or width) b in feet and displacement d in pounds, C is determined by the function C=4d^-1/3b.

a) Find the capsize screening value for the Tartan 4100 which has a displacement of 23,245 lbs and a beam of 13.5 ft.
for this one i came up with the answer c=1.89 this is how i got that please let me know if it is right
c=4(23245)^-1/3(13.5)
c=4(.035)(13.5)
c=.14(13.5)
c=1.89

now i have to solve for D how would i do that

Question

To be considered safe for ocean sailing, the capsize screening value C should be less than 2  For a boat with a beam (or width) b in feet and displacement d in pounds, C is determined by the function C=4d^-1/3b.

a) Find the capsize screening value for the Tartan 4100 which has a displacement of 23,245 lbs and a beam of 13.5 ft. 
for this one i came up with the answer c=1.89 this is how i got that please let me know if it is right
c=4(23245)^-1/3(13.5)
c=4(.035)(13.5)
c=.14(13.5)
c=1.89

now i have to solve for D how would i do that