Probability one plant yield exceeds another

When grown under the same conditions, two varieties of tomato plant have yields (the quantity of tomatoes produced) that are independent and approximately normally distributed.

Variety $\mathrm{A}$ has a mean yield of $6\text{ kg}$ per plant, with a standard deviation of $1.2\text{ kg}$.

Variety $\mathrm{B}$ has a mean yield of $5\text{ kg}$ per plant, with a standard deviation of $1.5\text{ kg}$.

The probability that a randomly selected tomato plant of variety $\mathrm{B}$ will have a higher yield than a randomly selected plant of variety $\mathrm{A}$ is closest to