Answer:
183,750
Step-by-step explanation:
Data provided in the question: 
Sales in the first quarter = 150,000 units
Increase in sales each quarter = 15000 units
Ending inventory = 25% of the current sales units
Now,
 Ending inventory of first quarter = 25% of Units produced in the first quarter
= 0.25 × 150,000
= 37,500
Units produced in the first quarter = Sales + Ending inventory of first quarter 
= 150,000 + 37,500
= 187,500
Units to be produced in the second quarter 
= Sales in second quarter - Ending inventory of first quarter + Ending inventory 
= [ 150,000 + 15,000 ] - 37,500 + 25% of [ 150,000 + 15,000 ] 
= 165,000 - 37,500 + 41,250
= 168,750
Units to be produced in the Third quarter 
= Sales in third quarter - Ending inventory of second quarter + Ending inventory 
= [ 150,000 + 15,000 + 15,000 ] - 41,250 + 25% of [ 150,000 + 15,000 + 15,000 ] 
= 180000 - 41,250 + 45,000
= 183,750