Estimate a venture's cash flow expected next year based on the following information: current year's net sales $=$ $$400,000$; firm value $=$ $$500,000$; constant future growth rate $=10\%$; and venture investors' required rate of return $=20\%.$

a$.$ $$50,000$

b$.$ $$40,000$

c$.$ $$60,000$

d$.$ $$80,000$

Please provide me with the equation for the BA$2$ Plus calculator method.