Can you explain on how to calculated and why?

Blue Fin started the current year with assets of $840,000, liabilities of $420,000 and common stock of $240,000. During the current year, assets increased by $480,000, liabilities decreased by $60,000 and common stock increased by $330,000. There was no payment of dividends to owners during the year. What was the amount of Blue Fin's change in total stockholders equity during the years?

a. $420,000 increase

b. $300,000 increase

c. $240,000 increase

d. $540,000 increase