What is the primary purpose of the SOLVER add$-$in in Microsoft Excel?

a$.$

SOLVER is a data validation tool used to restrict input values in a specified range.

b$.$

SOLVER is used to create pivot tables for data analysis and visualization.

c$.$

SOLVER assists in spell$-$checking and proofreading Excel documents.

d$.$

SOLVER is a feature for creating and editing macros in Excel.

e$.$

SOLVER is a tool for optimizing and solving complex mathematical models by adjusting input cells, subject to certain constraints.