A person may not engage in vaginal intercourse or a sexual act with another: without the consent of the other; if the victim is a substantially cognitively impaired individual, a mentally incapacitated individual, or a physically helpless individual, and the person performing the act knows or reasonably should know that the victim is a substantially cognitively impaired individual, a mentally incapacitated individual, or a physically helpless individual; or if the victim is under the age of 14 years, and the person performing the act is at least 4 years older than the victim. A person 18 years of age or older may not violate subsection (a)(1) or (2) of this section involving a child under the age of 13 years. Except as provided in paragraph (2) of this subsection, a person who violates subsection (a) of this section is guilty of the felony of rape in the second degree and on conviction is subject to imprisonment not exceeding 20 years. Subject to subparagraph (iv) of this paragraph, a person 18 years of age or older who violates subsection (b) of this section is guilty of the felony of rape in the second degree and on conviction is subject to imprisonment for not less than 15 years and not exceeding life. A court may not suspend any part of the mandatory minimum sentence of 15 years. The person is not eligible for parole during the mandatory minimum sentence. If the State fails to comply with subsection (d) of this section, the mandatory minimum sentence shall not apply. If the State intends to seek a sentence of imprisonment for not less than 15 years under subsection (c)(2) of this section, the State shall notify the person in writing of the State’s intention at least 30 days before trial.