`f_(0) = 2cm, f_(e) = 5cm, u_(0) =- 2.4 cm`
(a) `(1)/(v_(0))-(1)/(u_(0)) = (1)/(f_(0))`
`(1)/(v_(0)) - (1)/(-2.4) = (1)/(2)`
`(1)/(v_(0)) = (1)/(2) - (1)/(2.4) = (2.4-2)/(4.8) = (1)/(12) rArr v_(0) = 12 cm`
Tuber length: `L = v_(0) +f_(e) = 12 +5 = 17cm`
`m = (v_(0))/(u_(0)) .(D)/(f_(e)) = (12)/(-2.4) xx (25)/(5) =- 25`
(b) `(1)/(v_(e)) - (1)/(u_(e)) = (1)/(f_(e))`
`(1)/(-25) - (1)/(u_(e)) = (1)/(5) rArr -(1)/(u_(e)) = (1)/(5) +(1)/(25) = (6)/(25)`
`u_(e)=- (25)/(6)cm`
Tube length: `L = v_(0)+|u_(e)| = 12+(25)/(6) = (97)/(6) = 16.2cm`
`m =(v_(0))/(u_(0))(1+(D)/(f_(e))) = (12)/((-2.4)) (1+(25)/(5)) =- 30`