Because the variable cost is directly proportional to the number of software packages sold.

So the total variable cost of 50 sets is 50c.

Then 6=5+50c.

The solution is c=0.02 million yuan.

So the total cost y = 5+0.02x

(2) No loss means cost = total income.

The cost is y = 5+0.02x

Income i = 0.07x times

Then 5+0.02x = 0.07x.

The solution is x= 100.

So at least 100 sets will not lose money.