# PROBLEM LINK:

**Setter:** soumyadeep_21

**Testers:** tabr, tejas10p

**Editorialist:** hrishik85

# DIFFICULTY:

775

# PREREQUISITES:

None

# PROBLEM:

An electronics shop sells red and blue lamps. A red lamp costs X rupees and a blue lamp costs Y rupees.

Chef is going to buy **exactly** N lamps from this shop. Find the **minimum** amount of money Chef needs to pay such that at least K of the lamps bought are red.

# EXPLANATION:

Chef needs at least K lamps red.

The remaining (N-K) lamps can be red or blue.

Also - as per the constraints K \leq N

Hence the minimum amount to pay = (K \times X) + (N - K) \times (min (X,Y))

# TIME COMPLEXITY:

Time complexity is O(1).

# SOLUTION:

## Editorialist's Solution

```
t=int(input())
for _ in range(t):
N,K,X,Y = map(int,input().split())
print(K*X + (N-K)*(min(X,Y)))
```