PMMaterial planning price and operational variance.

Hi, I have a question on past exam December 2009. Please help me. I knew the formula to calculate material planning variance = ( revised price - standard price) * actual quantity used. Is this right? Actual quantity used= 35g * 100,000 cards = 3,500kg. So planning price variance = ( $4.8-$4) * 3,500= 2,800 A. But I saw in the answer the result is ( $4.8-$4) * 4,200kg= 3,360 A. I don't understand here why their actual quantity is 4,200kg. And operational variance =( actual price - revised price) * actual quantity used. So actual quantity used here is the same as quantity above. Their answer is ( $5.25- $4.8) *3,500kg. Why? Can you explain? Thanks. Question 1: Secure Net (SN) manufacture security cards that restrict access to government owned buildings around the world. The standard cost for the plastic that goes into making a card is $4 per kg and each card uses 40g of plastic after an allowance for waste. In November 100,000 cards were produced and sold by SN and this was well above the budgeted sales of 60,000 cards. The actual cost of the plastic was $5·25 per kg and the production manager (who is responsible for all buying and production issues) was asked to explain the increase. He said ‘World oil price increases pushed up plastic prices by 20% compared to our budget and I also decided to use a different supplier who promised better quality and increased reliability for a slightly higher price. I know we have overspent but not all the increase in plastic prices is my fault’ The actual usage of plastic per card was 35g per card and again the production manager had an explanation. He said ‘The world-wide standard size for security cards increased by 5% due to a change in the card reader technology, however, our new supplier provided much better quality of plastic and this helped to cut down on the waste.’ Required: Calculate planning and operational variances as the information allows.