Solution:Total employees in the company = 1800
Total number of employees in level 1 = (95/300) × 1800 = 95 × 6 = 570
Total number of employees in level 2 = (35/100) × 1800 = 630
Total number of employees in level 1 = 2 × total number of employees in level 4 + 90
2 × Total number of employees in level 4 = Total number of employees in level 1 - 90
Total number of employees in level 4 = (570 - 90)/2
Total number of employees in level 4 = 480/2
Total number of employees in level 4 = 240
Total number of employees in level 1 + Total number of employees in level 2 + Total number of employees in level 3 + Total number of employees in level 4 = 1800
570 + 630 + Total number of employees in level 3 + 240 = 1800
Total number of employees in level 3 = 1800 - 1440
Total number of employees in level 3 = 360
Salary of level 1 employee per month = Rs.20000
Salary of level 2 employee per month = 20,000 × 1.15 = Rs.23,000
Salary of level 3 employee per month = 23000 × 1.2 = Rs.27,600
Salary of level 4 employee per month = Rs.23,000 × 1.4 = Rs.32,200
Employees in level 1 = 570
Employees in level 2 = 630
Employees in level 3 = 360
Required average = (570 + 630 + 360)/3
= 1560/2 = 520