CONCEPT: The question uses the summation formula basics.

SOLUTION:
 

Sale on 8th Feb = 70.
With a minimum of 1 sold and different number of refrigerators sold each day,
we have the count of refrigerators sold in the 27 days as
1+2+3+4+....27 =(27 * 28 )/2
= 378

Total refrigerators sold in the month
= Count of refrigerators sold on 8th Feb + Count of refrigerators sold on the remaining days of the month
=70 + 378
=448 (OPTION D)