Answer:
Net income under variable costing would be $429,000.
Explanation:
Under the variable costing method the most important point to understand here is that fixed cost of the previous period ( 3000 units in this case ) would not be carried over to current period. Which means that the fixed cost and cost of goods sold be less now and the profit will increase.
NET INCOME =
 SALES                                   = $ 1035,000  ( 23,000 X 45 )
(-) COST OF GOODS SOLD  = ($ 391,000) ( 23000 X 17 )
  ( We have multiplied 23,000 units by 17 because now those fixed cost of $5 are not carried forward to this period)
GROSS CONTRIBUTION MARGIN  = $1035,000 - $391,000
                                                           = $644,000
 (-)VARIABLE SELLING AND ADMINISTRATION EXPENSES = ($69,000)
  ( $115,000 X 60% )
CONTRIBUTION MARGIN = $644,000 - $69,000
                                            = $575,000
(LESS) FIXED COSTS          = ($146,000)   [ $100,000 + $46,000 ]
1) MANUFACTURING COST = 20,000 X $5 
                                               = $100,000
2) SELLING AND ADMINISTRATION EXPENSES = $115,000 X 40% 
                                                                                 = $46,000
INCOME  = $575,000 - $146,000
                 = $429,000