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Chandu and his toy stack

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After setting up the area. Chandu wanted all his toys to be stacked there in that area. So that all of them are accessible easily. Currently, He is having *N* stacks of toys each with height \(H_1,H_2...H_n\) (assuming all toys are of same height).Chandu did not like the configuration much and want to change the height of each stack. To increase the height of a particular stack he can add some toys to it and to decrease the height he can take out some toys from that stack.
Chandu, knows that he requires ** X units of effort for putting up an item onto the stack** and

**Input**:

First Line of input contains an integer *t*, which is the number of test cases. then, *t* lines follow where first line of each test case contains three integers *N*, *X* and *Y* then *N* lines follow containing two integers each \(a[i]\) and \(b[i]\) (Initial height of \(i\;th\) stack and final height of \(i\;th\) stack.)

**Output**:

Output an integer which is the minimum effort required.

**NOTE**: he just need to make stacks of given height. Not necessarily each stack should be made from its corresponding stack.

**Constraints**:

\(1 \le t \le 100, \)

\(1 \le N \le 10^5, \)

\(1 \le a[i],b[i] \le 10^6\)

Explanation

Here, He is having *3* stacks initially of height \(3,1\) and *1*
He can take out one toy from first stack to get a stack with two toys with *4* units of effort.
He can put toy on second stack to get a stack with two toys with *6* units of effort.
Total effort = \(10\) units.
After the two operations he will have three stacks with required heights.

Time Limit:
1.0 sec(s)
for each input file.

Memory Limit:
256 MB

Source Limit:
1024 KB

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