To solve this problem you must apply the proccedure shown below:
1. The halving and doubling is a multiplication strategy which is very useful to simplify products.
2. You have the following multiplication given in the problem above:

3. Then, by applying this strategy, you have that the double of 50 is 100 and the half of 28 is 14. Therefore, when you multiply them, you obtain:

Therefore, the answer is:
.