Answer: The answers are given below.
Step-by-step explanation: Given in the question that Kent invested $5000 in a retirement plan. He allocated x dollars of the money to a bond account that earns 4% interest per year and the rest to a traditional account that earns 5% interest per year.
(A) Let, '$y' be the amount of money Kent invested in the traditional account, then we have
![y=5000-x.](https://img.qammunity.org/2020/formulas/mathematics/high-school/fk36hd5npzqk1fq516z4ou1rkem79blmxo.png)
This is the required expression.
(B) After 1 year, total money in the bond account will be
![M_b=x+(1* 4* x)/(100)=x+(x)/(25)=(26)/(25)x,](https://img.qammunity.org/2020/formulas/mathematics/high-school/93ef4lcb6p29ip2nhb5y1koecr71efv312.png)
and amount of money in the traditional account will be
![M_t=(5000-x)+(1* 5* (5000-x))/(1000)=(5000-x)+(5000-x)/(200)\\\\\\\Rightarrow M_t=(201(5000-x))/(200).](https://img.qammunity.org/2020/formulas/mathematics/high-school/dk21sq42z4geo74pphefkdji7al274l6ki.png)
Therefore, total amount invested after 1 year will be
![M=M_b+M_t=(26)/(25)x+(201(5000-x))/(200)=(208x+1005000-201x)/(200)\\\\\\\Rightarrow M=(7x+1005000)/(200).](https://img.qammunity.org/2020/formulas/mathematics/high-school/vjg6gozf1joj6sby3nbbuou4e9zhvs53yp.png)
(C) If x = $500, then we have
![M=(7* 500+1005000)/(200)=(1008500)/(200)=(10085)/(2)=5042.5.](https://img.qammunity.org/2020/formulas/mathematics/high-school/i09hm0ks6ulawxajp757byt0p9fj0312wo.png)
Thus, Kent will have $5042.5 in his retirement plan after 1 year.