Let's set up the equation based on the given information:

5% of M + 4% of N = (2/3) * (6% of M + 8% of N)

Now, let's simplify and solve for the ratio of M and N.

First, convert percentages to decimals:

0.05M + 0.04N = (2/3) * (0.06M + 0.08N)

Now, eliminate the fractions by multiplying both sides by 3 (the least common multiple of 3 and 2):

3 * (0.05M + 0.04N) = 2 * (0.06M + 0.08N)

Now, distribute on both sides:

0.15M + 0.12N = 0.12M + 0.16N

Next, let's isolate terms with M and N on different sides of the equation:

0.15M - 0.12M = 0.16N - 0.12N

0.03M = 0.04N

Now, divide both sides by 0.03 to find the ratio of M and N:

(M/N) = (0.04N) / 0.03M

(M/N) = (4/3) * (N/M)

Now, simplify the ratio:

(M/N) = 4/3

So, the ratio of M to N is 4:3. The correct answer is 4:3.