Probability Question?

An investor has $100,000 to invest this year. One option is to purchase a guaranteed investment certificate with a 1.8% yield. Another option is to purchase a risky stock. The investor believes that the stock will increase by 5% with probability 0.7, and will decrease by 3% with probability 0.3. Based on these assumptions, what should the investor do? Do you have any practical caveats for the investor?