If 90% of the Model-D Laptops produced in each year were sold by the company. then how many Model-D Laptops remained unsold? 

Given:

The total number of Laptops produced in 2019 was 35 lakh and in 2020, 1t was 44 lakhs.

Calculation:

For 2019, the number of Model-D laptops produced can be calculated as follows:

⇒ 35,00,000 x 10% = 3,50,000

And for 2020, the number of Model-D laptops produced can be calculated as follows:

⇒ 44,00,000 x 10% = 4,40,000

Now, let's find the number of Model-D laptops sold in each year:

For 2019, the number sold is 3,50,000 x 90% = 3,15,000

For 2020, the number sold is 4,40,000 x 90% = 3,96,000

And the number of unsold laptops for each year can be found by subtracting the number of sold laptops from the total number of produced laptops:

For 2019, unsold laptops = 3,50,000 - 3,15,000 = 35000

For 2020, unsold laptops = 4,40,000 - 3,96,000 = 44000

So the total number of unsold Model-D laptops = 35000 + 44000 = 79000.