I noticed these two images going around as "shares" on Facebook today.
Of course it had to be the Texas image that included the "Test Your Knowledge..." title.
Perhaps 94.5 The Buzz (the original poster of the image) should test their knowledge.
The choice of determiner is based on the initial sound of the word that follows it not whether or not the following word starts with a consonant or vowel.
Remember the rule - always use "a" before a word that begins with a consonant sound and "an" before a word that begins with a vowel sound.