Variance analysis

A company manufactures a single product. An extract from a variance control report together with relevant standard cost data is shown below.

standard s.p per unit $70
Standard d.m cost(5kg * $2per kg) $10 per unit
Budgeted total material cost of sales $2300 per month
budgeted profit margin $6900 per month

Actual results
sales revenue $15200
Total direct material cost $2400
DMPV $800 adverse
DMUV $400 favourable

no change in inventory levels

what was the actual production in february??

A 200
B 217
C 240
D 280

My working:

Actual material cost = 2,400
Standard material cost = 2400-800 = 1600 Since Standard cost per unit is $10.

Actual production = 1,600/10 = 160

BUT They calculated “Standard material cost” Like this = 2400-800+400=2000

Can you explain why is that so?

Thanks in advance