Jack, Marta, Rand, Todd and 6 more students went apple picking. Every two of these 10 students pick a different number of apples. Combined, the ten students pick 45 apples. Suppose Jack and Marta pick a total of 16 apples; Marta and Rand pick a total of 15 apples; Rand and Todd pick a total of 13 apples. How many apples did Todd pick