Two thin biconvex lenses have focal lengths $f_{1}$ and $f_{2}$. $A$ third thin biconcave lens has a focal length of $f_{3}$. If the two biconvex lenses are in contact,the total power of the lenses is $P_{1}$. If the first convex lens is in contact with the third lens,the total power is $P_{2}$. If the second lens is in contact with the third lens,the total power is $P_{3}$,then:

• A
  $P_{1}=\frac{f_{1} f_{2}}{f_{1}-f_{2}}, P_{2}=\frac{f_{1} f_{3}}{f_{3}-f_{1}}$ and $P_{3}=\frac{f_{2} f_{3}}{f_{3}-f_{2}}$
• B
  $P_{1}=\frac{f_{1}-f_{2}}{f_{1} f_{2}}, P_{2}=\frac{f_{3}-f_{1}}{f_{3}+f_{1}}$ and $P_{3}=\frac{f_{3}-f_{2}}{f_{2} f_{3}}$
• C
  $P_{1}=\frac{f_{1}-f_{2}}{f_{1} f_{2}}, P_{2}=\frac{f_{3}-f_{1}}{f_{1} f_{3}}$ and $P_{3}=\frac{f_{3}-f_{2}}{f_{2} f_{3}}$
• D
  $P_{1}=\frac{f_{1}+f_{2}}{f_{1} f_{2}}, P_{2}=\frac{f_{3}-f_{1}}{f_{1} f_{3}}$ and $P_{3}=\frac{f_{3}-f_{2}}{f_{2} f_{3}}$