Answer:
the post money valuation of the company is $1,750,000
Step-by-step explanation:
The computation of the post money valuation is shown below:
Given that
Value of 400,000 shares is $1 million. 
 So, 
The Value of 1 share is 
= $1 million ÷ 400,000 
= $2.5 
And, 
Total number of shares is 
= 400,000 + 200,000 + 100,000 
= 700,000 
Now 
Total value of shares is 
= $2.5 × 700,000 
= $1,750,000 
 hence, the post money valuation of the company is $1,750,000