Here's the typical flow of the Waterfall software development model:

Analysis: This phase focuses on defining the problem and gathering detailed requirements for the software. Understanding the specific mathematical operations to support is a key part of this phase.

Design: Designers turn the requirements from the analysis phase into a concrete blueprint for the software. This includes architectural and detailed design decisions covering how those mathematical operations will be implemented.

Implementation: Developers take the design and translate it into working code, writing the modules and functions to perform the calculations.

Testing: Testers verify the software to ensure it meets the requirements, including testing how the implemented calculator functions handle different operations.

Maintenance: Ongoing support after deployment to address bugs and introduce potential changes or enhancements.

Why the other options are less accurate:

A. Design and Testing: While testing validates the calculator's functions, the determination of the required operations happens earlier in the process.

B. Implementation and Testing: Implementation builds the calculator, but the specifications and choice of operations happen before coding starts.

C. Design and Implementation: Though closely linked, the design phase finalizes the operation choices before implementation begins.