Mulroney Corp. is considering two mutually exclusive projects. Both require an initial investment of $$10,600$ at $t=0.$ Project $x$ has an expected life of $2$ years with after$-$tax cash inflows of $$6,900$ and $$8,400$ at the end of Years $1$ and $2,$ respectively. In addition, Project X can be repeated at the end of Year $2$ with no changes in its cash flows. Project $Y$ has an expected life of $4$ years with after$-$tax cash inflows of $$4,600$ at the end of each of the next $4$ years. Each project has a WACC of $8\%.$ Using the replacement chain approach, what is the NPV of the most profitable project? Do not round the intermediate calculations and round the final answer to the nearest whole number.

a$.$ $$4,636$

b$.$ $$5,554$

c$.$ $$5,421$

d$.$ $$6,066$

e$.$ $$6,340$