Answer:
Value of the option to wait = $1,294,840
Explanation:
Gold = 39,200 ounces
Production per Year = 5,600 ounces
Total production in Years = 39,200/5,600=  7  
Required Rate Return = 10%
Initial cost =$33,600,000
- If the mine has been started today
After tax cash flow in a year = $1,360* 5,600 =   $7,616,000
Net Present Value = - $33,600,000 + $7,616,000*PVIFA(10%, 7 Years)
= - $33,600,000 + $7,616,000*4.8684 = $3,477,73
- If the mine will be started next year
Expected after tax cash flow = $1,560*55%+$1,260*45% =  $1,425/OUNCE
After tax cash flow in a year = $1,425 * 5,600 = $7,980,000  
Net Present Value after 1 Year= - $33,600,000 + $7,980,000*PVIFA(10%, 7 Years)
= - $33,600,000 + $7,980,000*4.8684 = $5,249,832
NPV  =    $5,249,832 / 1.10  =  $4,772.575
Option to wait = $4,772,575 - $3,477,734 =  $1,294,840