If the length of radius of a right circular cone be `r/2` unit and its slant height be `2l` unit, then total surface area will be -
(a) `2 \pi r (l+r)` sq. unit, (b) `\pi r (l + r/4)` sq. unit, (c) `\pi r (l+ r)` sq. unit, (d) `2 \pi r l` sq. unit