Funding for this research was provided by:
National Science Foundation (DMS-1814902, DMS-1411393)
Received: 11 September 2019
Revised: 20 January 2020
Accepted: 27 June 2020
First Online: 13 July 2020
Compliance with ethical standards
: On behalf of both authors, the corresponding author (SPS) asserts that there exists no conflict of interest regarding this article.