A polymer sample contains 10 molecules each with molecular mass 5,000 and 5 molecules each with molecular mass 50,000. The number average molecular mass of the polymer sample is

• Correct answer
  A

  $2 \times 10^4$
• B

  $3 \times 10^4$
• C

  $2 \times 10^5$
• D

  $3 \times 10^5$

Hence, the correct answer is option: 'A'.