I'm not quite sure where to start with this.
Thank you in advance
Looks okay, too many significant digits though.(a) Area of slick = [itex]\pi[/itex]r2
diameter of slick [you mean thickness of slick] = 2x1010
volume of slick= area x thickness
volume of oil=volume of slick= 1L = 0.001m3
M=850kg/m3 x 3.14x10-30m3
does that make sense?