How to find the linking number of 200bp circular DNA?

A 220 bp circular DNA adapts two right-handed turns of interwound supercoiling in aqueous solution. (a) Please describe the linking number, twist and writhe of this DNA. (b) In a solution of 30% ethanol, the DNA changes conformation from B-form to A-form helix. Please describe the linking number, twist and writhe of the above 220 bp DNA in 30% ethanol solution. (B-form DNA=10 bp/turn; A-form DNA=11 bp/turn)