Solution:
Let the cumulative costs of the plans will be equal after x months.
Then we can write
[tex]150+10x=50+300x\\ \\ 150-50=300x-10x\\ \\ 100=290x\\ \\ x=\frac{100}{290}\\ \\ x=\frac{10}{29}[/tex]
Hence after 10/29th Month cost will be equal.
and that cost[tex]=150+\frac{10}{29} *10=\frac{4450}{29}[/tex] $