Answer:
a) Original price= $420000
b) Saving= $ 42000.
Explanation:
Given: Purchase price of beach house= $378000
Price reduction= 10%
Let the original price be `x`
Now, computing to find the value of original price.
Purchase price=

⇒

⇒

⇒

Cross multiplying both side
∴ x=

∴ Original price= $420000.
Saving= Original price - Purchase price
Saving=

∴ Saving made by Mark and David is $42000.