Mixing two different essential oils to their maximum safe dilutions in one carrier oil

I want to mix cinnamon bark essential oil (safe at a maximum 0.5% dilution) with tea tree essential oil (safe at a maximum 15% dilution) in shea butter.

Shea butter is safe undiluted. The above maximum dilution percentages are if the essential oil comprises the given percentage of the total volume of the mixture and the remaining percentage is shea butter alone (i.e. a mixture of 0.5% cinnamon oil with 99.5% shea butter and a mixture of 15% tea tree oil with 85% shea butter respectively).

How do I find how much of each of these three substances to put together in a single mixture to achieve the maximum safe dilution of both the cinnamon bark and tea tree oils?

• You need to provide the definition of dilution. Assuming the dilution of $x$ is the weight of $x/$ weight of the mixture, $0.5$ parts cinnamon, $15$ parts tea-tree, $84.5$ parts shea butter should be the answer. – Shubham Johri Dec 16 '18 at 8:51
• Added! Thank you. – Wellesley Dec 18 '18 at 0:39