Which strategy is correct when simplifying the expression in the box?
(5^3)(5^-5)(5^7)
• Add the bases, and multiply the exponents to get 15^-105
• Add the bases, and add the exponents to get 15^5
• Keep the common base, and multiply the exponents to get 5^-105
•Keep the common base, and add the exponents to get 5^5